/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun<lingyun@email.com>
 *                  All rights reserved.
 *
 *       Filename:  socket_server_fork.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(09/03/25)
 *         Author:  LingYun <lingyun@email.com>
 *      ChangeLog:  1, Release initial version on "09/03/25 16:35:28"
 *                 
 ********************************************************************************/
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <getopt.h>
#include <ctype.h>

void print_usage(char *progname)
{
	printf("%s usage: \n", progname);
	printf("-p(--port): sepcify server listen port.\n");
	printf("-h(--help): print this help information.\n");

	return ;
}

int main(int argc, char ** argv)
{
	int                   sockfd = -1;
	int                   rv = -1;
	struct sockaddr_in    servaddr;
	struct sockaddr_in    cliaddr;
	socklen_t             len;
	int                   port = 0;
	int                   clifd;
	int                   ch;
	int                   on = 1;
	pid_t                 pid;

	struct option         opts[]={
		{"port", required_argument, NULL, 'p'},
		{"help", no_argument, NULL, 'h'},
		{NULL, 0, NULL, 0}
	};

	while( (ch=getopt_long(argc, argv, "p:h", opts, NULL)) != -1 )      //解析命令行参数
	{
		switch(ch)
		{
			case 'p':
				port=atoi(optarg);
				break;
			case 'h':
				print_usage(argv[0]);
				return 0;
		}
	}

	if(!port)                           //如果端口为空，调用print_usage()
	{
		print_usage(argv[0]);
		return 0;
	}

	sockfd=socket(AF_INET, SOCK_STREAM, 0);     //创建sockfd描述符

	if(sockfd < 0)                              //sockfd创建失败
	{
		printf("Creat socket failure: %s\n", strerror(errno));
		return -1;
	}
	printf("Creat socket[%d] successfully!\n", sockfd);   //sockfd创建成功

	setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));   //创建套接字，使端口可以被重用

	memset(&servaddr, 0, sizeof(servaddr));         //初始化sockaddr.in结构体，用于设置服务器ip端口等信息
	servaddr.sin_family=AF_INET;
	servaddr.sin_port = htons(port);
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

	rv=bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));   //rv存储bind()绑定sockfd的返回值
	if(rv < 0)
	{
		printf("Socket[%d] bind on port[%d] failure:%s\n", sockfd, port, strerror(errno));
		return -2;
	}

	listen(sockfd, 13);         //监听端口，成功返回0，失败返回-1
	printf("Start to listen on port [%d]\n", port);
	while(1)                    //进入循环
	{
		printf("Start accept new client incoming...\n");      

		clifd=accept(sockfd, (struct sockaddr *)&cliaddr, &len);        //创建新的文件描述符clifd用于已经成功监听的端口
		if(clifd < 0)           //clifd创建失败
		{
			printf("Accept new client failure: %s\n", strerror(errno));
			continue;
		}

		printf("Accept new client [%s:%d] successfully\n", inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port));   //clifd创建成功

		pid = fork();           //创建子进程
		if(pid < 0)             //子进程创建失败
		{
			printf("fork() creat child process failure: %s\n", strerror(errno));
			close(clifd);
			continue;
		}
		else if(pid > 0)        //若父进程先运行，关闭clifd，使子进程先运行
		{
			close(clifd);
			continue;
		}
		else if(0 == pid)       //子进程运行
		{
			char          buf[1024];
			int           i;

			printf("Child process start to communicate with socket client...\n");    //子进程开始和服务器通信

			close(sockfd);      //关闭父进程的sockfd

			while(1)            //子进程通信循环
			{
				memset(buf, 0, sizeof(buf));
				rv=read(clifd, buf, sizeof(buf));
				if(rv < 0)
				{
					printf("Read data from client sockfd[%d] failure:%s\n", clifd, strerror(errno));
					close(clifd);
					exit(0);
				}
				else if(rv == 0)
				{
					printf("Socket[%d] get disconnected\n", clifd);
					close(clifd);
					exit(0);
				}
				else if(rv > 0)
				{
					printf("Read %d bytes data from Server:%s\n", rv, buf);
				}

				for(i=0; i<rv; i++)         //将rv中小写字母变为大写
				{
					buf[i]=toupper(buf[i]);
				}

				rv=write(clifd, buf, rv);
				if(rv < 0)
				{
					printf("Write to client by sockfd[%d] failure: %s\n", clifd, strerror(errno));
					close(clifd);
					exit(0);
				}
			}//Child proccess loop
		}//Child process Start
	}

	close(sockfd);

	return 0;
}

